1. Field of the Invention
The present invention relates to a clamshell-type electrophotographic image forming apparatus, and more specifically to a clamshell-type electrophotographic image forming apparatus which reliably holds a photosensitive drum that is detachably attached to a clamshell opening/closing unit.
According to the present invention, the photosensitive drum and the developing device in the clamshell-type electrophotographic image forming apparatus are constructed in the form of cartridges so that they can be detachably attached, facilitating the cleaning and inspection of the photographic image forming apparatus and enabling the cartridges to be renewed safely and reliably after they are used a predetermined number of times.
2. Description of the Prior Art
There has heretofore been provided a clamshell-type electrophotographic image forming apparatus in which a clamshell opening/closing unit is mounted on a base plate so as to be opened and closed, and a drum cartridge by which the photosensitive drum is supported is detachably accommodated in the clamshell opening/closing unit.
With the drum cartridge being detachably attached, it is possible to closely inspect the interior at the time of checking and cleaning as well as to independently remove the drum cartridge from the apparatus to conduct the checking and cleaning, enabling an operator to carry out the operation very efficiently.
There have further been provided electrophotographic image forming apparatus in which the photosensitive drum and the developing device are contained in a single detachable unit, or a unit containing the photosensitive drum and a unit containing the developing device are detachably attached, so that the interior of the electrophotographic image forming apparatus can be easily and reliably checked and cleaned and that the parts can be replaced. Heretofore known solutions however were not satisfactory.
There is a limit in the number of times of using the photosensitive member for forming images; i.e., the photosensitive member must usually be renewed after it is used, for example, after 10,000 times, 30,000 times or 50,000 times. There also exists a limit in the number of times of using the developing means for forming images; i.e., the developing means must be renewed after being used for a predetermined number of times.
Further, the developing device has been constructed in a unit which permits the developing means only to be detachably attached but does not permit the toner feeding tank or the toner feeding device to be removed. Or the developing device has been constructed in such a system that the toner contained in the developing means is used without particularly providing the toner feeding device, so that the developing means is renewed when it is depleted, the used developing means being discarded.
With the photosensitive drum and the developing device being detachably attached as described above, it is possible to closely inspect the interior of the image forming apparatus at the time of checking and cleaning. Moreover, the individual units can be independently taken away to the external side facilitating checking and cleaning and enabling the operation to be carried out very efficiently. Further, there are limits in the number of times for using the units which, therefore, must be renewed after they are used a predetermined number of times.
The drum cartridge by which the photosensitive drum is supported is inserted in the clamshell opening/closing unit from a side in which it is opened, and is pulled out in a direction opposite to the direction in which it was inserted. The drum cartridge inserted in the clamshell opening/closing unit is not limited for its position in the direction in which it is taken out. Therefore, when the clamshell opening/closing unit is closed, the position of the photosensitive drum is deviated to adversely affect the formation of image.
The photosensitive member and the developing means have durability for maintaining images of good quality, durability being determined roughly by the number of times for forming the images. These members must be renewed before their durability ends, and the interior of the image forming apparatus must be checked and cleaned before the durability ends such that the apparatus maintains proper functions at all times. These operations should desirably be carried out correctly without requiring skill through a simple procedure. For this purpose, it has heretofore been attempted to contain the photosensitive member, developing means and accessories thereof in a cartridge to facilitate the attachment, detachment, checking and cleaning.
However, the developing roller (developing sleeve) of the developing device is nearly in contact with the surface of the photosensitive drum, and both ends of the sleeve are in many cases in contact with the surface of the photosensitive drum. Under such a condition, if the cartridge for the photosensitive drum and the cartridge for the developing device are separately attached or detached in the same direction, the surface of the drum and both ends of the developing sleeve come into rubbing contact with each other to damage the surface of the drum. Should that happen, the operation of checking and cleaning loses becomes meaningless, and the finished image is deteriorated causing a serious problem. In order to prevent disturbance caused by the rubbing between them, one method consists of accommodating the photosensitive drum and the developing means in a single cartridge. This unitary structure, however, causes a problem in that checking cannot be effected closely, and the cleaning and checking involve difficulty and become incomplete.
Furthermore, in order to check and clean the image forming apparatus and to maintain high image quality at all times, it is better that important units such as the photosensitive drum and the developing device are independently attachable and detachable and that the units have further been divided.
In practice, however, when a drive gear of the developing unit is in mesh with a drive gear of the main body, it becomes difficult to attach or detach the developing unit. Moreover, the photosensitive drum is scarred when the developing unit is attached or detached under the condition where the drum cartridge supporting the photosensitive drum has been mounted.